Levi Colwill said Chelsea were left "hurt" by the margin of defeat as they were thumped 3-0 by Brentford at the Gtech Community Stadium.
The visitors were much improved defensively in the first half following some shaky displays, looking not half as chaotic at the back and in midfield as they have done at times this season.
Everything then changed when poor making at a corner in the 61st minute allowed Jaidon Anthony to head in unmarked from virtually on the goal-line before further goals from Igor Thiago and Fábio Carvalho condemned the Blues to a hiding.
"It was tough," Colwill said. "Conceding from a set-piece isn't the best and then we tried to push and maybe over-exposed ourselves and played some passes we shouldn't and forced it.
"I feel we needed to relax and not push too hard for the equaliser. We needed to believe it would come if we continued playing our football. But I think we pushed too hard to get it and they hurt us on the counter.
"They get the second goal and then the third goal really hit home and hurt. The second half we weren't good enough, obviously and we've got a lot to work on during the international break."
Chelsea's excellent goal-scoring form was brought to an abrupt end as Brentford marshalled their injury-hit forward line superbly.
The absence up front of João Pedro was hard to ignore, his replacement Danny Welbeck not quite so able to act as the middle link in a fluid trio with Cole Palmer and Morgan Rogers.
Both forwards were involved and looked dangerous, but they operated far less in combination than when Pedro is present.
It left Xabi Alonso's side, who had scored 18 times in six matches in all competitions ahead of Friday's west London derby, looking strangely out of sorts, with little apparent attacking threat.
"We can't rely on the front three to pull us out of danger," Colwill said. "The rest of us have to try to help as much as possible. The defence, the midfield and the attackers, we all need to help each other much more.
"We've definitely got a lot of room to improve."
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The result left Alonso as only the sixth manager in Premier League history have two or more goals scored against his side in each of his first five matches.
Previously only Mick McCarthy, Sammy Lee, Terry Connor, Slavisa Jokanovic and Scott Parker had begun life in the division with such frailty at the back.
Brentford were rampant after going in front. In the 83rd minute, Kevin Schade ran clear and was denied by Emiliano Martínez, but there to knock in his first league goal of the season on the rebound was Thiago.
Substitute Carvalho made it three in stoppage time from Schade's cross.
